We can identify that an index which is dropped is temporary only if it is prefixed with "SESSION.". It is therefore not possible for the exception which is described:
\[~pierre-yves.nicolas], this is possible because if you have a look to the exceptions, you'll see that the index was created earlier on a temporary table.
Ok, it may be doable but that would make the rule implementation much more complex. What if the create statement is located in another file?
Moreover, I suppose that this exception would be rarely used: a temporary index is usually created on a temporary table, and the temporary index is rarely dropped explicitly because it is implicitly dropped when the temporary table is dropped.
